Conventionally known is a wireless communication system that performs a communication between wireless stations or between wireless terminal devices via a relaying station like a repeater station. In order to utilize radio waves when wireless communication is carried out, it is necessary to establish a wireless station and a repeater station which intervenes between wireless stations or between wireless terminal devices must be licensed. At this time, a call sign that is unique identification information is given to the repeater station.
It is obligated for the repeater station to transmit a call sign that is given thereto as unique identification information at a center frequency of a licensed and allocated frequency band for each certain time in utilizing radio waves. The call sign transmitted from the repeater for each certain time is used for monitoring whether or not the quality of radio waves matches the rules like regulations, for monitoring whether or not operation of a wireless station is carried out appropriately in accordance with the rules like regulations, and for checking the utilization situation of the radio waves.
According to the technology disclosed in patent literature 1, a radio-wave-monitoring controlling unit uses a clock to monitor a radio wave level periodically, operates a frequency changing unit to change a frequency to be monitored, receives radio waves induced at an antenna in a set frequency through a radio-wave-monitoring receiving unit, and detects the radio wave level of the received radio waves through an electric wave level detector. It is distinguished whether or not the received radio waves are disturbing waves or communication radio waves by comparing demodulated waves demodulated by a demodulator with a reference radio wave used to carry out wireless communication. The process for monitoring radio waves is executed at a certain cycle through a timer function by the clock, and is successively executed for each communication frequency range for each cycle.
Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. H08-70271